In a large-sized video camera called one for business-use or for professional-use such as TV camera, a battery cell or a pack combining a plurality of battery cells and a substrate are stored between a rear cover and a top cover, which are secured to each other by welding, adhesive bonding, or the like, as shown in e.g. patent document 1. For example, covers divided in two are pressurized and heated by ultrasound to be melted and solidified for joining. The battery pack formed as described above has such features that it can be configured to have a simple structure and to be compact and staunch as compared with covers that are screw-fastened to each other for fixation and thus can be manufactured inexpensively.    [Patent Document 1]
International Publication WO01/073879